This initial open-label, pilot study will be performed in approximately 24 patients with RA who have who have achieved some therapeutic benefit from treatment with concomitant etanercept and MTX for a minimum of 3 months, but the response must be an incomplete response, and patients must have a minimum of 9 tender and 6 swollen joints while receiving concomitant etanercept and MTX. It will assess safety and evidence of therapeutic benefit of infliximab in this patient population. The study will examine any differences in the pharmacokinetics and immunogenicity of etanercept and infliximab in patients who are incomplete responders to etanercept.